Java Basics Review First day

Foreword: read so many people's blog article, and subscribed to a lot of bloggers of the public number, they have written the idea of the blog, but by various excuses to blow (for example, the language does not have words, etc.), have not been able to adhere to, think oneself is enough. Today, from the beginning of the basic knowledge of Java review, regularly write blog, is to give yourself a cruel and confessed! You insist, say a word to yourself: look for yourself.

Key Words: JAVA environment variable constant variable

Features of 1.Java: Simplicity, object-oriented, portability.

2.Java is a combination of compiled and interpreted languages, mainly because:

A. Using the editor to write Java source programs---> Xxx.java files---> B. Compiling java source files---> Xxx.class files---> Using the compiler (JAVAC command) the virtual machine (interpreter, Java command) to interpret the execution.

3. Easy to mix two times words: JRE = Jvm+java Core Class library, JDK = JRE + Java development tool. If you only need to call Java, follow the JRE. If you want to do Java development, you have to install the JDK, the URL is: http://www.oracle.com/technetwork/java/javase/downloads/ jdk8-downloads-2133151.html, download the installation, the current version is: Jdk8u40.

Three main features of the 4.Java operating environment:

The load code (completed by the ClassLoader-class loader)---> Code checksum (done by the byte Validator-bytecode verifier)---> Execute code (done by the runtime interpreter-runtime interpreter).

5.Java Development Environment Construction Note: The meaning of% in%java_home% is the meaning of the connector. (Java_home,%java_home%\bin;)

6. Note, it is necessary to write, do not write the comments of the programmer is not a good programmer, "rookie" is not to write comments, do not write comments are not acceptable.

There are three types of comments in Java, that is, single-line comments-//, multiline comments-*/*/, document comments. There are multiple lines of comments (/*/), not nested, and the following code cannot be commented upon when the kinsoku is recognized.

eg. /* Java is a cool/*/* * * * * * * * language, language cannot be commented.

7. Update the understanding of path and classpath in the environment variable configuration at night.

PS: Everything starts hard, since the beginning, you insist on, you understand.

Java Basics Review First day